Microbiome Management in dogs & cats
Two bowls on the kitchen floor, filled at the same time each day. Once eaten, each meal travels through a different digestive system, with its own microbial community.
Illustration. Dog and cat drawn at the same body length, not to scale.
Why this setting matters
A dog and a cat often share a kitchen, a routine and the person who fills both bowls. What each needs from its bowl is not the same.
The dog’s bowl
Dogs make plenty of the pancreatic enzyme that digests starch, and handle starchier food better than cats do.2
Worth noticing
The cat’s bowl
Cats need animal protein and fat in their food and do best on diets low in starch. A finding in dogs does not transfer to them automatically.2,3
Worth noticing
In both animals, what is not digested earlier reaches the large intestine. There, microbes ferment undigested fibre and protein, and those microbes affect the stool an owner sees.2
What is happening inside
A dog and a cat, and the microbial community in each one’s large intestine.2
Resources, physical conditions and management.
Functions and interactions within the community.
What can be measured in the host or wider system.
Dog
Observable function Faecal score and body condition score
Cat
Observable function Faecal score and body condition score
Why this system is investigated. Dietary biology is the background: what a dog or a cat eats sets what reaches its large intestine and the microbes there. The research question is separate: what a humic or fulvic material does in a living dog or cat. The one humic record in this collection is a cell-culture study, pig intestinal cells and immune cells from one dog, and it did not study a living animal, which is where the question remains.
Two digestive environments
Dog and cat share the plan of the tract. What arrives in it, and what each animal can do with it, differs.1,2
Dog
Cat
Key, numbered the same in both diagrams
An early compartment in food processing.
The main site of digestion and nutrient absorption.
Microbes ferment undigested fibre and protein, and water is absorbed.
The final passage before elimination.
Simplified digestive anatomy. Diagrams are not to scale, and no size difference is drawn between the species.
A stool sample provides information about material leaving the tract. It does not directly describe every digestive compartment or explain every digestive sign.
The framework in companion animals
Within the framework, Digestive Stability describes appropriate digestive function and the capacity to adapt through change.
For dogs and cats, the discussion begins with the individual animal’s usual pattern and the context of any departure from it.
What observations are usual for this animal, and which changes deserve attention?
How do observations change through a feeding or routine transition?
Following disruption and any necessary care, how does function change over time?
Digestive Stability is a working concept, not a diagnosis or a single test result. Consistent-looking stool alone does not establish that every aspect of digestive health is normal.
What is established
One feeding study in dogs and one in cats show how quickly, and how differently, gut microbes respond to a change of diet. They are context for reading any study in these animals. Neither tested a humic or fulvic material, and neither is an ingredient trial.
Dogs
A longitudinal study examined faecal microbial and metabolite measurements after an abrupt dietary change in healthy adult dogs. It reported shifts followed by stabilisation in the measurements studied.
Limitation. Twelve laboratory Beagles followed for 13 days after each change; stability was described from five sampling days rather than tested formally.
Funding. USDA and NomNomNow; three authors are employed by or hold stock options in NomNomNow.
Interpretation. The study concerns the tested diets and healthy adult dogs. It does not establish a universal transition period, validate the project’s Digestive Stability concept or justify abrupt diet changes in routine care.
Cats
Li and Pan studied dietary protein-to-carbohydrate ratios in lean and overweight or obese adult cats. They reported differing faecal microbial responses, with more pronounced compositional changes in the overweight or obese group.
Limitation. Thirty-nine colony cats with one faecal sample per phase, on diets designed by the funder's staff; microbial functions were predicted from 16S data, not measured.
Funding. Nestlé Purina PetCare; both authors are Purina employees.
Interpretation. The findings illustrate why population and dietary context matter. They do not establish a supplement effect, a weight-management recommendation or a universal ideal microbial profile.
In this collection. Two background records on diet in dogs and cats, one laboratory cell study, and no study of a humic or fulvic material in a living dog or cat.
What is being investigated
Laboratory studyCell cultureNo living animal
Researchers tested a leonardite humic acid on two kinds of cells grown in culture: a layer of pig intestinal cells, and immune cells taken from one healthy dog. No dog or cat was fed anything.6
The dog’s immune cells
Challenged with bacterial endotoxin, the cells released less TNF-α at 24 hours. By 48 hours the difference was gone. A second signal, IL-6, showed only a trend.
The pig intestinal cell layer
The sonicated form of the preparation did not make the layer leakier. The non-sonicated form did, at 48 hours. How the material was prepared changed the result.
These cells were not a dog’s intestine, and the study does not show an effect in a living dog or cat. Whether these materials feed particular gut microbes, deliver nutrients or remove unwanted compounds in an animal are questions for studies in the animal itself.
What was administered, how was it characterised and prepared, and were other ingredients present?
Was the work conducted in dogs or cats, at what life stage and in what health context?
Did the study measure digestive observations, microbial changes, absorption or another response?
Humic acid lowered TNF-α from dog immune cells challenged with endotoxin at 24 hours, but not at 48 hours, and the IL-6 change was only a trend.
Limitation. A cell-culture study using pig intestinal cells and immune cells from one dog; it does not show an effect in a living animal.
Funding. Hungarian public research funding; no conflicts declared.
What to document about a dog’s or cat’s food, routine and digestive observations, so that a change can be read in context.
A useful digestive history includes the whole feeding pattern and recent circumstances, rather than the main food alone.
Main diet, treats, chews, table food, supplements and access to other animals’ food.
Meal pattern, actual intake where known, water access and shared feeding arrangements.
Moving home, boarding, travel, household changes and shifts in daily routine.
Age, relevant health history, prescribed diets, medications and professional recommendations.
Record observations consistently and identify which animal they belong to. Include changes in food, routine and care alongside changes in digestive function.
| Area | What to document |
|---|---|
| Food | Main diet, treats, extras and any recent changes. |
| Appetite | Amount offered and eaten where known, and changes from the usual pattern. |
| Stool | Consistency, frequency and other visible changes using a consistent description. |
| Other digestive observations | Vomiting or regurgitation as reported, without assuming they have the same cause. |
| Body condition | Trends assessed consistently and discussed with the veterinary team where appropriate. |
| Daily context | Household, travel, boarding, medication and care changes. |
In a shared household, avoid attributing food intake, stool or vomit to a particular animal unless the observation is reliable.
Persistent or concerning digestive changes need veterinary assessment. Do not delay care while testing a supplement, and do not discontinue a prescribed diet or medication without veterinary guidance.
Where to learn or contribute
Coming soon · Fulgenix
Companion Animals
Why lasting digestive health begins with the environment inside the gut, not with adding one more thing.
We welcome contributions to educational review, evidence interpretation and the development of relevant evaluations for dogs and cats.
Associated brand. Fulgenix, run by the project’s founders, sells products for dogs and cats. No study on this page tested a Fulgenix product.
How the project relates to its brandsPrepared by Carbon Biome Project, 19 October 2026; revised 22 October 2026. External scientific review of this page has not been completed.
